Portable Fire Extinguishers Practice Test

Recognizing extinguisher agents by their formulation helps you understand what you’re using in a fire. This setup—potassium bicarbonate as the active base with inert diluents like mica, Fuller's earth, and amorphous silica—is characteristic of Purple K. The potassium bicarbonate base is what makes it effective on flammable liquid (Class B) and electrical (Class C) fires, while the mica, Fuller's earth, and silica act as anti-caking agents and flow aids to keep the powder free-flowing and dischargeable through the extinguisher nozzle. The combination of these specific additives distinguishes Purple K from other powders.

Monoammonium phosphate is the base of many ABC dry chemical powders, but not potassium bicarbonate-based; Aqueous film forming foam is a liquid concentrate for foam suppression, not a dry powder; and BC dry chemical powders use bicarbonates but typically don’t feature this exact mix of diluents.